Generally, various processes such as a thin film deposition process, an etching process, and a thermal process are repeatedly carried out on a substrate subject to these processes, for example, a semiconductor wafer (simply referred to as a wafer, hereinafter) to produce integrated circuits on the wafer in a fabrication process of semiconductor integrated circuits. In addition, predetermined post-treatments may also be carried out on the wafer that has undergone each of the processes. As the post-treatments, there may be a process for cleaning the wafer, an example of which is a residue removal process for removing residues remaining on the wafer, a process for measuring process results, an example of which is a thickness measurement process, a particle measurement process, and the like.
Such treatments are carried out in a substrate process apparatus including process chambers that are configured so that a predetermined process such as a plasma process and a measurement process can be carried out. The substrate process apparatus includes, for example, a transfer robot having a pivotable and retractable transfer arm for transferring the wafer. Generally, a susceptor on which the wafer is placed is provided in the process chambers and the wafer is transferred between the susceptor and the transfer arm.
In order to appropriately carry out a process on the wafer placed on the susceptor, the wafer has to be placed in an accurate position without horizontal (X- and Y-directional) displacements. To this end, when the displacements are found after a wafer position is first detected, the displacements are corrected in order to correct the wafer position.
In recent years, an imaging component such as a charge coupled device (CCD) camera has been used in order to accurately detect the wafer position. Namely, an image of a wafer circumference portion is taken by the imaging component, and wafer displacement is detected in accordance with the obtained image data (see Patent Document 1, for example). When the wafer displacement is detected in accordance with the image data obtained by the imaging component, coordinates of the imaging component need to be accurately determined on reference coordinates (XY coordinates) in advance. Conventionally, the X-axis direction, the Y-axis direction, and the origin position of the reference coordinates have been determined in accordance with a design-based position of the imaging component and the like.    Patent Document 1: Japanese Laid-Open Patent Application No. 2002-280287    Patent Document 2: Japanese Laid-Open Patent Application No. 2003-50106